Photos with Animal Crossing was revealed at Hyper Japan 2015, and is basically the same thing as the Photos with Mario app released a year ago, but with Animal Crossing characters. Download the free app from the eShop, then use the AR cards to take photos with them.

It will only be available until September.

I'm not disappointed because it was probably just a quick little app and wasn't even developed by the Animal Crossing team. (EAD 1 made Photos with Mario so I'm assuming it's the same for this)